Dementia: high blood pressure could reduce alzheimer's risk

Experts have revealed the onset of the condition - which is also known as hypertension - in later life may actually protect against Alzheimer's Disease. High blood pressure is generally

thought to increase dementia risk. But now researchers have said the onset of high blood pressure later in life is associated with lower dementia risk after the age of 90, especially if

hypertension is developed at age 80 or older. Professor Maria Corrada, of the University of California, Irvine, author of the study, revealed the results. She said: "In this

first-of-its-kind study, we find that hypertension is not a risk factor for dementia in people age 90 or over, but is actually associated with reduced dementia risk. "This relationship

had not yet been examined in groups of older people in their 80s or 90s, known as the 'oldest old'." Researchers followed 559 people for an average of 2.8 years to investigate

the link between dementia, age of hypertension onset, and blood pressure measurements. All participants are from a long-term study of people age 90 and older known as The 90+ Study. None of

the participants - who had  an average age of 93, had dementia at the start of the study. They received dementia assessments every six months during the study period. During the follow-up

period, 224  - 40 per cent -  of the participants were diagnosed with dementia. The researchers found that participants who reported hypertension onset at age 80 to 89 were 42 per cent less

likely to develop dementia after the age of 90 compared to those who reported no history of high blood pressure. Participants whose high blood pressure began at age 90 or older were at even

lower risk -  63 per cent less likely to develop dementia. The researchers said the associations were ‘statistically significant’. They said dementia risk declined as the severity of

hypertension increased - concluding that hypertension could protect the brain from processes which lead to dementia. Dr Maria Carrillo, Alzheimer's Association Chief Science Officer,

said: "These new findings suggest some risk factors for dementia may change over the course of our lives. We have seen similar results in past studies comparing body mass in older

adults with dementia risk." A study published in 2008 of 255 people aged 75 or older living in Stockholm, Sweden, found those who were overweight had a lower dementia risk. A study

published in 2009 of almost 3,000 adults near age 75 on average who were part of an observational studyhad similar results - those whowere underweight had an increased risk for dementia

while those who were obese had a reduced risk. Professor Corrada said: "Before we can make the leap to suggesting changes to blood pressure recommendations for reducing dementia risk in

clinical care, we need more research to confirm and explain our findings. "This includes investigations into the underlying biology of hypertension and brain function." She said

there were several potential reasons for the link between hypertension and dementia risk observed in the study. These include that blood pressure may need to reach a certain level to

maintain adequate blood flow to the brain, and that this level may change with age. The research was published online in the journal Alzheimer's and Dementia.